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Research group of Dr. Arturo S. Leon

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Illinois Transient Model (ITM)


[New]The version 1.5.3 of the ITM model was released on May 8 of 2015. The current version of ITM was developed at University of Houston (Texas).

The ITM model is a free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

The Illinois Transient Model (ITM) is a multipurpose Finite Volume (FV) model to analyze transient flows in closed-conduit systems ranging from dry-bed flows to gravity flows, to partly gravity-partly surcharged flows (mixed flows) to fully pressurized flows (waterhammer flows). In the ITM model, the free surface region is modeled using the 1D Saint-Venant equations and the pressurized region is modeled using the 1D compressible waterhammer equations.  The current version of the ITM model has features that make this model superior with respect to other models for analyzing transient flows in complex closed-conduit systems. The first feature is that the ITM model can simulate all possible flow regimes in complex closed-conduit systems. In particular, the ITM model can accurately describe positive and negative open channel-pressurized flow interfaces, interface reversals, and it can simulate sub-atmospheric pressures in the pressurized flow region. The second feature is that the ITM model can simulate transient mixed flows when large pressure wave celerities (~1000 m/s) are used. The latter is very important when pressurized transient flows are of interest. If transients are of no interest, a small pressure wave celerity may be used to speed up the computations.


The ITM model was used for several projects. These applications include:
  • Impact of gates closure in the formation of transient flows in combined sewer systems
  • Potential for surge formations
  • Hydraulic transients for the simultaneous occurrence of free surface and pressurized flows in closed-conduit systems
  • Analysis of reservoir filling in combined sewer systems ranging from dry-bed flows, to free surface flows, to partly free surface flows-partly pressurized flows, to fully pressurized flows.


The ITM model can simulate dry-bed flows, pure free surface flows, pure pressurized flows and the simultaneous occurrence of free surface and pressurized flows in circular closed-conduit systems (transient and non-transient conditions). The boundary conditions currently supported include dropshafts, reservoirs, rating curves, closing and opening of gates (open channel or pressurized) as a function of time, and junctions with any number of connecting pipes and any type of horizontal and vertical alignment. The model can also simulate flows in adverse slopes.


The Illinois Transient Model (ITM) was used worldwide for the analysis of combined sewer systems in the United States of cities such as Chicago, Omaha and Dallas and worlwide in countries such as Switzerland, New Zealand and Mexico.

Below is an incomplete list of users:

Metropolitan Water Reclamation District of Greater Chicago (MWRD), Illinois

Metropolitan St. Louis Sewer District, Missouri

Dr. Martin Rüdisüli (Martin.Ruedisueli@hunziker-betatech.ch), Hunziker Betatech AG, Switzerland

Dr. David H. Axworthy (DAxworthy@nhcweb.com), http://www.nhcweb.com/, Pasadena, California

Sam Glovick (sglovick@WadeTrim.com), Wade Trim,  Pittsburgh, Pennsylvania

Tony Margevicius (TMargevicius@water.co.nz), URS, New Zealand












3/15/16 (New)
ITM model Version 1.5.4 Executable (Includes four input files)
ITM User's Manual Version 1.5 (PDF)


Source Code V. 1.5 (Hydraulics and SWMM-modified interface)

Technical Support

For technical support please contact Arturo Leon (aleon3@Central.UH.EDU).

A fee of $250 per hour is charged for technical support, which is used for continuing the developement of ITM (student tuition and student stipends). All payments are routed through University of Houston. The payment form can be found here.

Training fee: $2000 per day plus costs of hotel and plane tickets.

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This page has been updated on July 21, 2018 11:41 PM

Copyright ©  Arturo Leon, All Rights Reserved.